In the Old Testament, the kidneys as well as other internal organs represented the seat of emotions. Therefore, by presenting these parts of the animal, the worshipper was symbolically surrendering their own deepest emotions and intentions to the Lord. “In this part of the ritual,” one commentator remarks, “offerers were symbolically surrendering themselves—their innermost beings—to the Lord” (Ross p.118).
4 and the two kidneys with the fat that is on them at the loins, and the long lobe of the liver that he shall remove with the kidneys.